The present invention claims the benefit of application no. 199.56.503.1, filed on Nov. 24, 1999, in Fed. Republic of Germany.
1. Field of the Invention
The present invention relates to a bone substitute material comprising living cells and a setting matrix. The invention likewise relates to processes for producing such a bone substitute material and to the use of hydroxyapatite cement for producing a bone substitute material containing living cells, and the use thereof in a suitable injection apparatus.
2. Description of the Related Art
It is desirable with many bone defects to have available a bone substitute material with which these defects can be filled. Examples of such defects in the jaw region are periodontosis or atrophies, in the hand region are defects after bone tumor resections and trauma and defects of the spine, the skull and the long bones, for example associated with osteoporotic fractures and tumor resections.
Various bone substitute materials are known in the prior art. Bone substitute materials which can be molded are often referred to as xe2x80x9cinjectable bonexe2x80x9d. Solutions covered by this term to date comprise either hydrogels with bone-forming cells, hydrogels with osteoinductive proteins or polymers which solidify in situ, with or without osteoinductive factors. Each of these solutions has specific disadvantages. Either the materials contain no bone-forming cells, and thus are unable to have osteogenic effects. Ordinarily, a biomaterial or bone cement is injected into a bone defect as homogeneous filling which cannot be absorbed and replaced by bone. Mechanical stress leads to fatigue and fracture of the implant.
Although materials which comprise cells display potential osteogenicity, they have no stability. It is moreover not possible to shape these materials, usually in the form of hydrogels, and they have no plasticity. Polymers which set in situ often have toxic effects on the cells. U.S. Pat. No. 5,914,121 discloses a composition for implantation into a mammal comprising fibroblasts, hydroxyapatite powder and fibrin. This composition displays no secondary stability because the material does not solidify after implantation but continues to be deformable. The reason for this is that ceramic hydroxyapatite powder is used. This composition does not set because the particles do not bind together with one another. There is no prior art bone substitute material which comprises living cells and thus is able to have osteogenic effects and, at the same time, provides adequate secondary stability.
There is thus a pressing need for an advantageous bone substitute material.
The object has been achieved by the bone substitute material of the invention, which comprises a soft matrix, living cells and a setting matrix. We have developed a suitable mixing and application unit for the bone substitute material of the invention which displays excellent primary and secondary stability. The primary stability (also xe2x80x9cprimary plasticityxe2x80x9d) of a bone substitute material means the stability of a composition at the time of application. The bone substitute material of the present invention is plastically moldable and can be converted into specific three-dimensional shapes depending on anatomical requirements. The material is thus not too xe2x80x9cfluidxe2x80x9d because it would then be impossible to shape any plastic structures. However, it is not too rigid either, even hardening completely in the extreme case, because it would then be impossible to adapt easily to the circumstances of the case, and because such xe2x80x9chardxe2x80x9d implants normally could not contain any osteogenic components. Secondary stability means the stability of the implant after the intervention. The bone substitute material of the invention retains the three-dimensional shape conferred on it for a long time after setting. It is stable to pressure. This is achieved by the fact that the material of the invention, which has previously been shaped appropriately, completely sets within a relatively short time.